Synthesis, Characterization, Swelling Properties, and Biological Applications of Ph-Sensitive Polymeric Hydrogels based on Citric Acid, Triethanolamine, and 2-Furoic Acid

Abstract

Introduction: The objective of this endeavor is to create novel hydrogels utilizing three monomers namely Citric acid (CA), Triethanolamine (TEA), and 2-Furoic acid (FA). Citric acid (CA), a crosslinking agent that can overcome the toxicity and connects with other crosslinking substances. FTIR analysis shows that the synthesis of hydrogels based on triethanolamine and citric acid leads to the esterification reaction of carboxylic acid of citric acid with hydroxyl group of triethanolamine to the formation of pre-polyester. The pre-polyester combines with 2-Furoic acid results in hydrogel formation.H¹-NMR and C¹³NMR spectroscopy of the hydrogels have been examined which conforms the ester bond formation. Investigations on swelling and swelling equilibrium were carried out at various pH ranging from 2.0 to 11.0. The swelling e quilibrium was improved by increased CA composition in hydrogels for pH levels of 2.0, 4.0, 7.0, 9.0, and 11.0 than acidic media. The percentage of swelling is larger in neutral (pH 7.0) and alkaline (pH 9.0) medium. With increasing anionic charge, the ionic strength of the medium and the degree of crosslinking are increased and the swelling capacity consequently decreases in pH 11. The hydrogel has shown strong antibacterial activity against Escherichia coli (gram negative) and moderate inhibition in Staphylococcus aureus and Bacillus subtilis(gram positive) bacteria. The antifungal studies were carried out with C.albicans and A.nigerresults into inferior antifungal action with respect to the standard clotrimazole 20 mg/well. Further, cytotoxic studies have also been carried out. The results reveal moderate activity with respect to Ascorbic acid. In overall aspects, the hydrogels of present investigation may be recommended for biomedical applications.

Objectives: To synthesis CTF based biopolymeric hydrogel which is having considerable antibacterial and antioxidant property for biomedical recommendations.

Methods: The monomer, 0.020 mol citric acid (3.842 g) was dissolved in ethanol and placed in a round-bottomed flask equipped with a mechanical stirrer. Triethanolamine [0.020 mol (2.640 g)] dissolved in ethanol was added drop wise using a dropping funnel. The mixture was stirred for one hour at 140 °C. The completion of the pre-polyester reaction was indicated by the formation of a sticky white gel-like compound Citric acid-Triethanolamine (CT). Subsequently, 2-furoic acid (0.020 mol, i.e., 2.241 g) dissolved in ethanol was added to the pre-polyester CT at 140 °C and stirred constantly for 2 hours. The formation of a glassy brown gel (CTF) indicated the completion of the reaction.

Results: The pre-polyester combines with 2-Furoic acid results in hydrogel formation.H¹-NMR and C¹³NMR spectroscopy of the hydrogels have been examined which conforms the ester bond formation. Investigations on swelling and swelling equilibrium were carried out at various pH ranging from 2.0 to 11.0. The swelling e quilibrium was improved by increased CA composition in hydrogels for pH levels of 2.0, 4.0, 7.0, 9.0, and 11.0 than acidic media. The percentage of swelling is larger in neutral (pH 7.0) and alkaline (pH 9.0) medium. With increasing anionic charge, the ionic strength of the medium and the degree of crosslinking are increased and the swelling capacity consequently decreases in pH 11. The hydrogel has shown strong antibacterial activity against Escherichia coli (gram negative) and moderate inhibition in Staphylococcus aureus and Bacillus subtilis(gram positive) bacteria. The antifungal studies were carried out with C.albicans and A.nigerresults into inferior antifungal action with respect to the standard clotrimazole 20 mg/well. Further, cytotoxic studies have also been carried out. The results reveal moderate activity with respect to Ascorbic acid.

Conclusions: The percentage of swelling was significantly higher at alkaline pH (9.0) compared to acidic pH.The swelling equilibrium of the polymeric hydrogels has shown increased water absorbency with increasing citric acid concentration. The CA₄ hydrogels showed mild inhibition in gram negative bacteria Escherichia coli. Antioxidant studies have shown that lower concentrations of both furoic acid and citric acid exhibit better activity compared to higher concentrations. The present Cytotoxic studies exhibits the IC₅₀ in 80 µL in Ethanol for  TEA₁ and CA₁ hydrogels, then remaining hydrogels shows IC₅₀ in 100 µL in Ethanol. Lower the concentration of FA, TEA and CA, higher the toxicity and higher the concentration of FA, TEA and CA lower the toxicity is studied.